Nuclear spin interferences in bulk water at room temperature

Nuclear spin interference effects generated in a macroscopic sample of 10ml degassed water are detected in a simple NMR experiment. A \pi/2 - \tau - \pi/2 RF double pulse sequence (Ramsey sequence) is applied to the water sample immersed in a static magnetic field B0 " 4.7T. For a homogeneity of B0 of the order of \Delta B0/B0 = 2 . 10^{-8}, the nuclear spin interference term is controlled with a maximum relative deviation of 9.7 %. These results are a first step to manipulation of nuclear spin coherence of water molecules

Metastable Solid and Liquid Helium-4

This manuscript presents the experiments done in the group "Quantum solids and fluids" of Laboratoire Kastler Brossel in Paris since I joined the group in 2009. This group was created in 2003 by Philippe Jacquier and Jacques Dupont-Roc joined him in 2004.We are interested in the metastable phases of condensed 4He.The fascinating phase diagram of 4He at low temperatures is shown in the figure below. Several features in this diagram are unique compared to that of all other simple elements. The most striking one is that there is no triple point (liquid-gas-solid coexistence point) in the phase diagram of 4He meaning that it is possible to cool a liquid-gas mixture of 4He all the way down to T ! 0 K. Below T = 2.17 K, liquid 4He is in its famous superfluid state which is understood as a mixture of two fluids: a superfluid part with zero entropy and viscosity and a normal fluid which carries the heat content. [...

Expériences d'optique atomique cohérente ou non avec un jet superfin d'atomes métastables de gaz rares

In this thesis, we present a new type of atomic source: an ultra-narrow beam of metastable atoms produced by resonant metastability exchange inside a supersonic beam of rare gas atoms. We used the coherence properties of this beam to observe diffraction of metastable helium, argon and neon atoms by a nano-transmission grating and by micro-reflection-gratings. Then, we evidenced transitions between Zeeman sublevels of neon metastable 3P2 state due to the to the quadrupolar part of van der Waals potential. After we showed experimental proofs of the observation of this phenomenon, we calculated the transition probabilities in the Landau - Zener model. We discussed the interest of van der Waals - Zeeman transitions for atom interferometry. Last, we described the Zeeman cooling of the supersonic metastable argon beam (3P2). We gave experimental details and showed the first time-of-flight measurements we got of slowed atoms.Dans cette thèse, on présente un nouveau type de source atomique: un jet superfin d'atomes métastables produit à partir de l'échange de métastabilité au sein d'un jet supersonique d'atomes de gaz rares. On a utilisé les propriétés de cohérence de ce jet pour observer la diffraction de l'hélium, de l'argon et du néon métastables par un nano-réseau par transmission et par des micro-réseaux par réflexion. Ensuite, on a mis en évidence des transitions entre sous niveaux Zeeman du niveau 3P2 du néon métastable, transitions dues au terme quadrupolaire de l'interaction de van der Waals entre l'atome et la surface. Après avoir montré les résultats expérimentaux, nous avons calculé les probabilités de transitions dans le modèle de Landau–Zener puis discuté de l'intérêt des transitions vdW-Zeeman pour l'interférométrie atomique. Enfin, on a décrit le procédé de ralentissement Zeeman du jet supersonique d'argon métastable (3P2) et montré les premiers spectres de temps de vol d'atomes ralentis obtenus